Phenol-formaldehyde resin and polyamide composition



Patented June 19, 1945 UNITED STATES PATENT OFFlCE PHENOL-FORMALDEHYDE RESIN AND POLYAIVIIDE COMPOSITION Gordon T. Vaala, Wilmington, DeL, assignor to E. L du Pont de Nemo urs & Company, Wilmington, Del., a corporation oi Delaware No Drawing. Application April 3, 1944,

. Serial No. 529,408

8 Claims. '(01. 260- 13) resin, has previously been'proposed. There has been, however, no disclosure heretofore either of polyamide compositions comprising the selected resins disclosed herein, or of the specific properties described hereinafter which are imparted to the fiber-forming polyamide com- 15 position and which markedly enhance its utllity..

This invention has as an object a new and I useful composition of matter. A further object is a modified fiber-forming polyamide composition which is capable of being readily spun from melt. or otherwise formed, into filaments, bristles, films, ribbons, rods, tubes, etc., and the like hav-,

ing improved properties. A further object is the manufacture of articles of this kind, and particularly of bristles and films, which have greater water resistance and which are markedly stiller than like articles previously obtained from fiber-forming polyamide compositions. Other ob; jects will appear hereinafter.

The above objects are accomplished in the so manner more fully pointed out hereinafter by incorporating'with the fiber-forming polyamides certain phenol-aldehyde resins.

The polyamides used in the practice of this invention are the fiber-forming or synthetic linear super-polyamides described in U. S. Patents 2,071,250, 2,171,253 and 2,130,948. The must i useful or these polymers for the present purpose are the polyamides which are obtainable from either polymerizable nonoaminomonocar- 40 boxylic acids or their amide-forming derivatives, from the reaction of diamines with dicarboxylic acids or amide-forming derivatives of dibasic carboxylic acids, or from mixtures of these types of polyamide-forming reactants. It is to be understood that the term "polyamide includes linear polymerscontaining other groups, as for instance the ester-amide interpolymers obtained by reacting an hydroxy acid with a dibasic acid and a diamine. The amine groups in the polyamides form an integral part of the main chain of atoms in the polymers. Upon hydrolysis with mineral acids thepolyamides revert to monomeric amide-forming reactants. For example, a. polyamide derived from a m mme and dibasic acid as yields on hydrolysis with hydrochloric acid the dibasic acid and the diamine hydrochloride. In the case of the amino acid polymers the amino derivatives are obtained in the form of the hydrochloride. These polyamides are remarkable in that'they can be formed into filaments which upon application of tensile'stress below the melting point, referred to as cold drawing, yield fibers exhibiting by characteristic X-ray patterns orientation along the fiber axis. Films and sheets, which may be obtained by extrusion from the molten polyamide, likewise exhibit orientation upon rolling or cold drawing.

I have discovered that fiber-forming compositions which yield filaments of useful pliability but of stiffness especially adapted to bristle manufacture, which filaments are not only water resistant but of sufliciently light color for textile fibers, and may be spun successfully without danger of infusibility of'the polyamide composition at melt spinning temperatures, are obtained by mixing a fiber-forming polyamide with selected phenol-formaldehyde resins.

The phenol-formaldehyde resins suitable for carrying out my invention do not become infusible within aperiod of 1 to 3 hours at a temperature of to 270 C. and are compatible with polyamides in all proportions. obtained by reacting with formaldehyde a monohydric phenol containing at least one, but not more than two substitutable positions ortho and para to phenolic hydroxyl, the ,substituents on theremaining ortho and para positions being hy. drocarbon radicals of at least & carbons attached to the phenol nucleus through a carbon atom carrying not more than one hydrogen atom. One method of imparting the desired properties of fusibility and compatibility with polyamides to these resins is to prepare them in the presence of an' acid catalyst and with a formaldehyde to phenol molar ratio of less than 0.9:1.0, preferably between 0.5:1.0 and 0.85:1.0. Examples of suitable phenols are p-t-butyl phenol, p-hydroxydiphenyl, o-cyclohexylphenol, p-cyclohexylphenol, p-t-octyl phenol (p-di-isobutyl phenol), o-t-amyl phenol, p-t-amyl phenol, p-t-hexyl phenol, 2,4,-

di-t-amyl phenol, etc.

ments, bristles, and films by extrusion from the molten polyamide-resin mixtures puts the phenol-formaldehyde resin to a severe test since the molten mixture is at a temperature considerably above those encountered in the preparation of phenolic resins or in the uses to which these resme are normally put.

Such resins are usually greater than 30%, the phenol-aldehyde modified polymers can be formed into filaments and films which can beoriented by cold drawing.

The new compositions of matter described herein are obtained by intimately mixing the preformed fiber-forming polyamide with the phenol-formaldehyde resin by fusion or in a mutual solvent. or bypreparing the polyamide in the presence of the phenol-formaldehyde resin. as for instance by intimate mixing of the polyamide-forming reactants or compositions, e. g.

the diamine-dicarboxylic acid salt, with the pulverized phenol-aldehyde resin and then proceeding with the polymerization of the polyamideforming reactants or composition in the regular fashion. Usually no viscosity stabilizing agent is necessary since a polyamide polymerized to a high degree is desired. The addition of the phenol-aldehyde resin gives a final product with a melt viscosity of the same order of magnitude as for an unmodified polyamide that has been stabilized.

The following examples, in which parts are by weight, illustrate. the preparation and appli cation of the products of this invention.

Example I An intimate mixtureof 678 parts of hexamethylene diammonium adipate and 146 parts of a p-hydroxydiphenyl formaldehyde resin was Dreparedand charged into a stainless steel autoclave. During a two-hour period the autoclave was heated to an internal temperature of 270 C., the pressure rising to 250 lbs/sq. in. During the next half-hour the pressure was reduced to atof elasticity of 0.30X10 and absorbed 7.4% of their weight of water at saturation, as contrasted with values of 0.17x 10 for modulus and 7.6% for water absorption for unmodified polyhexamethylene adipamide.

Example 111 An intimate mixture of 524 parts of hexa-- methylene diammonium adipate and 50 parts of a p-t-butylphenol-formaldehyde resin was prepared by ball-milling the ingredients. This mixture was charged into a stainless steel autoclave and during a two-hour period the autoclave was heated to an internal temperature of .270 C. while thepressure rose to 250 lbs/sq. in. During the next half-hour the pressure was reduced to atmospheric, following which the autoclave was maintained at an internal temperature of 270 C. for an additional hour. The modified polymer was then extruded in bristle form. The bristles were light yellow in color and softened at 245-250 C. They had a modulus of elasticity of 026x10 and absorbed 6.8% of their weight of water at saturation.

The resin used in this example was prepared by reacting for 12 hours at 100-110 C. with a small amount of concentrated hydrochloric acid as the catalyst, a mixture of one mole of p-t-butylphenol with 0.85 mole of formaldehyde, used as the commercial aqueous solution. The product is a light colored resin which remains fiuid when heated at 240 C. for four hours. A colorless, likewise non-heat hardening resin, is obtained when 0.7 mole instead of 0.85 mole of formaldehyde is reacted with 1 mole of p-t-butylphenol under the same conditions.

mospheric by permitting the water of the reaction to escape, following which the autoclave was maintained atan internal temperature of 270 C. for an additional hour. The modified polyamidethus obtained was then extruded from melt in bristle form. The bristle was yellow in color and softened at 200230- C. It has a modulus of elasticity (measure of stiffness) of 037x10 when saturated with water, and absorbed 5.7% of its weight of water at saturation, as contrasted with values of 0.17x 10 formodulus of elasticity and 7.6% for water absorption for unmodified poiyhexamethylene adipamide bristle.

The resin used in this example was a commercial, non-heat hardening p-hydroxydlphenylformaldehyde resin (BR-254). There may be used instead with similar results a resin prepared by heating for 7 hours at 120-130 C. a mixture of 1 mole of p-hydroxydiphenyl and 0.7 mole of formaldehyde (used as the commercial aqueous solution) in the presence of a small amount of concentrated hydrochloric acid.

Ezcample I! formaldehyde resin of Example I was heated for Example IV A mixture of 105 parts of hexamethylene diammonium adipate and 10 parts of an o-cyclohexylphenol formaldehyde resin was prepared and heated to 210 C. for two hours in a sealed tube. The mixture was then heated for two hours at 275 C. under an atmosphere of carbon dioxide.

The final product was pinkish in color and softened at 245-250 C. It could be molded to a stiff film which absorbed 5.8% of its weight of water at saturation. Bristle prepared from the .modifled polymer had a stiffness of 0.31 10 at saturation.

The resin used in this example is prepared by heating at 90-100 C. for 12 hours a mixture of 1 mole of o-cyclohexylphenol with 0.7 mole of formaldehyde (as the 37% aqueous solution) in the presence of a, small amount of concentrated hydrochloric acid. The resin remains fluid when heated at 240 C. for 4 hours. Instead of 0.7 mole of formaldehyde, there may be used' 0.9 mole per mole of phenohand even somewhat more.

Example V Polymer prepared as described in Example 1, consisting of approximately parts of polyhexamethylene adipamide and 20 parts of the p-hydroxydiphenyl-formaldehyde resin of Example I was injection molded using a standard commercial injection machine and a standard commercial two-cavity comb die. At temperatures of about 260 C., the polymer molded to combs of v and adipic acid.

good strength, stillness, and appearance. The combs were light colored rather than dark as are most phenol-formaldehyde molded articles.

Example VI A mixture of 60 parts of hexamethylene diammonum adipate, 40 parts of epsilon-aminocaprolactam, and 11 parts of p-hydroxydiphenyl-formaldehyde resin was heated at 250-260 C. for five hours in an autoclave. The product was then solute pressure of about 2 mm. The final product was light colored and melted at 150-l60 C. It absorbed 9.2% of its weight of water at saturation as compared with 14.5% for polyamide prepared in the same manner without the phenolic resin.

The resin of this example was prepared from p-hydroxy-diphenyl (1 mole), formaldehyde (0.7 mole) and hydrochloric acid catalyst as described in Example I.

Example VII 1 Five parts of a 20% solution-in hot butyl alcohol of a polyamide derived from hexamethylene diamine, decamethylene diamine, adipic acid, and sebacic acid was mixed with three parts of a 20% solution of a commercial, non-heat hardening p-hydroxy-diphenyl-formaldehyde resin (KR-254) in hot butyl alcohol. The mixture was compatible. Films were prepared by flowing the mixture on a hot plate and removing the solvent by heating for one hour at 100 C.

The polyamides in the foregoing examples may be replaced by any of those mentioned in the patents previously referred to. and include poly- Phenols in addition to those previously mentioned from which the phenol-formaldehyde resins may be derived are p-t-heptyl phenol,- o-theptyl phenol, 2,4-di-t-butyl phenol'etc.

Phenols of-the special type described give, when condensed with aldehyde (e. g., formaldehyde) resins which are non-heat hardening and com- "patible with polyamides, provided thefollowing procedural requirements are observed.- It is aerator been illustrated. Non-heat hardening phenol/alheated for two hours at 250 -260" 0. under an abof widely different properties.

dehyde resins are known in the art. see for example J. Ind. Eng. Chem. 33, 966-971, (1941) and somepf them are commercial products such as the Bakelite Co. resins 133-254 and Bit-4026.

The compositions of this invention may desirably contain for some purposes various modifying agents such as plasticizers. resins, cellulose derivatives, pigments, fillers, dyes and the like.

The present invention makes possible the preparationof modified fiber-forming polyamides These products,-

- depending upon their properties, are useful in teeth, etc.); heat resistant handles for utensils.

necessary that the formaldehyde/phenol molar ratio be less than 0.9:1.0. Preferably, this ratio is between 0.5:l.0 and 0.85:1.0, and still more 'preferably between 0.6:1.0 and 0.8:1.0. The desirable ratio depends partly on'the molecular weight of the phenol to be qondensed,"it being in general indicated to use less formaldehyde as the molecular weight of the phenol increases. -Another requirement is that the condensation be carried out in the presence of an acidiccatalyst e. g., hydrochloric acid, sulfuric acid, p-toiuenesulfonic acid, oxalic acid, ammonium chloride, etc. Any suitable aldehyde may'be used, e.'g.. acetaldehyde or butyraldehyde, but formaldehyde is preferred. The resins so prepared remain fusible on heating for 1 to 3 hours, and even much longer in most cases, at temperatures of 'l80to 270 C. Several preparations of such resins have specific embodiments thereof many forms and for many purposes. Typical applications are yarns, fabrics, bristles, rods, tubes, films. .sheets, molded articles, electrical insulation (e. g., for wires used as windings in electric motors), and coating compositions.

' The modified polyamides described herein are markedly superior to the unmodified polyamides from the standpoints of stiffness and water resistance, these properties being particularly desirable'in bristles for use in tooth brushes. These properties, are also important in connection with certain fllm uses, e. g. photographic films, since they permit the use of thinner films than is otherwise possible. These properties also enhance the utility of the polymer in molding. p rticularly injection molding. A further advantage is that the phenol-aldehyde ingredient is a comparatively low cost material which means that the modified polyamides can be prepared at lower cost than unmodified polyamides.

In addition to the uses already mentioned, polyamides modified according to the process of this dentures (base, artificial teeth, reinforcement for surgical instruments, radiator valves, etc.; sterilizable, unbreakable utensils; molded solid sheets,

etc.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the except as defined in the appended claims.

1. A composition of matter comprising a fiberformin'g synthetic. linear polyamide and a compatible phenol-formaldehyde resin which does not become infusible within a period of 1 to 3 hours at a temperature of to 270 C., said phenolformaldehyde resin being present in an amount oi from 1% to 30% by weight of said polyamide and being derived from. a monohydric phenol containing at least one but not more than two substituta'ble positions ortho and para to phenolic hydroxyl, the substituents on the remaining ortho and para positions being hydrocarbon radicals of at least 4 carbons attached to the phenol nucleus through a carbon atom carrying not more than one hydrogen atom, and said polyamide being 'the reaction product ofa linear polymer-forming composition comprising reacting materials selected from at least one of the groups consisting of (a) monoaminomonocarboxylic acid, and (b). I mixtures of diamines and dibasic carboxylic acids,

said phenol-formaldehyde resin being the condensation product in the presence of an acid catalyst of formaldehyde and said phenol in a molar ratio of formaldehyde to phenol less than 2. The composition of matter set forth in claim 1 in which said substituents comprise an aliphatic tertiary hydrocarbon radical in the para position to the phenolic hydroxyl.

3. The composition of matter setforth in claim 1 in which said phenol is o-cyclohexyl phenol.

4. The composition of matter set forth in claim 1 in which said phenol is p-tertiary butyl phenol.

5. The composition of matter set forth in claim 1 in which said phenol is p-hydroxydiphenyl.

6. The composition set forth in claim 1 in which said polyamide is polyhexamethylene adipamide.

7. Aprocess for preparing polyamide compositions of improved water resistance which comprises heating linear polyamide-torming, material under polymerizing conditions in the presence of a phenol-formaldehyde resin which does not become 'intusible within a period of from 1 to 3 hours at a temperature of 180 to 270 C., and which is derived from a monohydric phenol containing at least one but not more than two substitutable positions ortho and para to phenolic hydroxyl, the substituents on the remaining ortho and para positions being hydrocarbon radicals of at least 4 carbons attached to the phenol nucleus through a carbon atom carrying not more than one hydrogen atom, said polyamide-iorming material being selected from one of the groups consisting of (a) monoaminomonocarboxylic acid, and (b) mixtures of diamines and dibasic carboxylic acids, said phenol-formaldehyde resin being the condensation product in the presence of an acid catalyst of "formaldehyde and said phenol in a molar ratio of formaldehyde to phenol less than 0.9:1.0.

8. The process set forth in claim 7 in which said polyamide-iorming material comprises hexamethylenediamine and adipic acid.

GORDON T. VAALA. 

